1. Field of the Invention
The invention relates to a method for the treatment of mineral fillers using organic phosphate treatment agents.
The invention also relates to the mineral fillers so treated and that can be suspended in a polyol.
The invention also relates to such suspensions of these treated mineral fillers in polyols, as well as to their use in the manufacture of flexible, semirigid, or rigid polyurethane foams.
Finally, the invention relates to the use of flexible, semirigid, or rigid polyurethane foams containing these treated mineral fillers in the manufacture of molded or nonmolded objects.
2. Description of the Prior Art
To decrease the cost price per liter and per kilogram of molded or nonmolded objects made from flexible, semirigid, or rigid polyurethane foams, it has been increasingly necessary to increase the quantity of filler present in the flexible, semirigid, or rigid polyurethane foams while at the same time preserving or improving their physicochemical properties, such as, compression, or their aesthetic or other properties, such as fire retardation, which are desired in various fields of industry such as, notably, transports (for example, cars and furniture) and in construction or other fields.
Several methods exist today to introduce mineral fillers, such as calcium carbonate, into these polyurethane compounds.
In a first type of method (French Patent No. 2,651,238), calcium carbonate is introduced into a plasticizer for polyurethane. However, this method for obtaining a suspension of a filler in a plasticizer, which permits increasing the content of the filler in the polyurethane compound, is not suitable for the following reasons. Its cost is high and its use is excessively difficult in the manufacture of flexible, semirigid, or rigid polyurethane foams. In addition, the physicochemical properties of the foams obtained from such suspensions are degraded.
Applicants have invented a method which completely favors the introduction of mineral fillers into flexible, semirigid, or rigid polyurethane foams using an inexpensive, simple means that does not result in any problems involving a significant decrease in the reactivity of the polyurethane foams.
Applicants' method is an improvement over other methods for the introduction of the filler into the polyol, one of the constituents of the polyurethane, that are known to a person skilled in the art.
A first type of method discloses grafting of methacrylic acid (German Patent Nos. 2,654,746, 2,714,291, and 2,739,620) or of another vinyl compound such as styrene on the polyol. However, this type of method does not allow the use of a suspension of calcium carbonate in the polyol because the suspension is too difficult to handle as a result of an excessively high viscosity and a poor distribution of the filler in the medium.
Another type of method involves treating the filler at the surface prior to its introduction into the polyol by means of an agent that is, for example, an alcohol with 8-14 carbon atoms (French Patent No. 2,531,971) or a hydroxycarboxylic acid phosphate (European Patent No. 0,202,394).
However, these methods produce the same type of drawbacks as those cited above since the user is confronted with problems of poor dispersibility--in the polyol--of the mineral filler so treated.
Thus, the techniques heretofore known do not solve the problem of suspending mineral fillers in the polyol, which mineral fillers are intended to be used in the manufacture of flexible, semirigid, or rigid polyurethane foams.